Arduino 16: Magnetic Levitator Optically Controlled
Here’s the latest project, an optically-controlled magnetic levitator using the Arduino.
The OSEPP Uno clone runs a sketch which senses the position and velocity of the levitated object, and sends a switching signal to a power mosfet which switches a high-current pulse to the electromagnet coil. The program also samples and corrects for changes in ambient light, and allows you to change a stability parameter over the serial line while the system is running. Clever programming from Simon Monk (link below).
I found a bunch of Arduino levitators using Hall Effect sensors, but I didn’t have any in my boxes, so I wanted to see if an optically-sensed system would work well. I searched and found this one which was set up originally with a phototransistor sensor, but mine turned out to be too sensitive so I changed to a CdS photoresistor along with a 10k fixed resistor wired together as a potentiometer and used the voltage output of that to feed to the Arduino.
Here’s where I found the program sketch. I’m using it as-is, except I bumped up the starting value of “B” to 160. I’m still not sure if I’ve got the optimum value but the system as shown is pretty stable.
http://www.dangerouslymad.com/projects/chapter-13-levitation-machine
Thanks, Simon, “dangerouslymad”, whoever you are! The program is pretty clever. I wish I could afford to buy your books….
